This invention relates to electron tubes and, more particularly, to a channel-type electron multiplier.
The invention will have many uses. Therefore, its scope of application is not to be limited to the uses specifically disclosed herein.
In the past, it has been the practice to use image intensifiers or image converters to aid night vision for military reconnaissance or the like. Such tubes employ a photocathode which supplies a channel-type electron multiplier with primary electrons. The multiplier includes a glass plate with holes therethrough which support secondary emission. Primary electrons enter a hole and bombard the internal surface of the hole. Then, secondary electrons are emitted which travel part way down the hole and bombard it again. Each time, the number of secondaries exceed the bombarding numbers; and electron multiplication occurs. Thus, the multiplier produces an electron output which is far higher than its input. The output is then directed onto a phosphor screen which produces an image of the scene being viewed. The image is displayed with a brightness considerably greater than the scene itself would appear to the naked eye.
Electrons are accelerated down the plate holes by an electric field. The field is created by the application of different potentials to a conductive layer on each side of the glass plate. Each layer has holes in registration with the plate holes.
Fair resolution is obtained by using a relatively large number of small multiplier holes located close together. Thus, the output of each hole supplies a piece of the image picture.
Manufacture of channel-type electron multipliers with good resolution is difficult because of the requirement for a large number of small holes. Further, resolution is thereby limited. There is thus a continuing demand for channel-type electron multipliers of improved resolution.